This invention relates to an adhesive adapted for use in adhering a flooring product to a subfloor. The adhesive is particularly suitable bonding hardwood flooring products, such as laminated and solid hardwood planks, strips and blocks to, for example, plywood, oriented strand board (OSB), and concrete subfloors. The adhesive is characterized by having reduced density, enhanced homogeneity, reduced cost and improved spreadability.
The adhesive, which will be supplied to the installer in the form of a spreadable mastic, is intended as a substitute for conventional chlorinated solvent adhesives which have been or will be banned, and for water-based adhesives which have relatively high water content. The most popular chlorinated adhesives, such those containing 1,1,1, trichloroethane, contain no water and provide a permanent and aggressive bond between the flooring product and subfloor. However, they are messy to apply, expensive and have an unpleasant odor. Present water-based mastics, including one made by applicant, have between 20-40 percent water. When wooden flooring is applied to the mastic, the water soaks into the back of the wood, causing dimensional changes such as separation and lifting of adjacent flooring elements. While these conditions may under optimum conditions disappear over time, such water-based adhesives are in any event generally less tacky and not as aggressive as solvent-based adhesives.
A desirable mastic adhesive should have low water content of approximately 10 percent or lower. The mastic should also have moderate strengthxe2x80x94approximately 25-30 lb/in2 when fully cured, high flexibility and be rebondable to itself for about one week. Other desirable characteristics include environmental safety, easy application, low odor, and quick initial bonding. Further explanation and discussion of the advantages of the new ashesive according to this application are set out below.
The adhesive is based generally on the use of high-solids acrylic and vinyl-acetate ethylene polymers in combination with one or more tackifiers.
According to the invention, a gas-producing agent such as hydrogen peroxide is introduced into the mastic adhesive during manufacture. The hydrogen peroxide reduces the density of the mastic without affecting is strength, improves spreadability and assists in homogenizing the mixture.
Therefore, it is an object of the invention to provide a flooring adhesive which has a low water content and reduced density.
It is another object of the invention to provide an adhesive which is environmentally safe.
It is another object of the invention to provide an adhesive which is easier to spread.
It is another object of the invention to provide and adhesive which has enhanced homogeneity.
It is another object of the invention to provide an adhesive which is lower in density.
It is another object of the invention to provide an adhesive which has strength sufficient to permanently bond with and support a flooring product on a subfloor.
It is another object of the invention to provide and adhesive which retains a high degree of flexibility when fully cured.
It is another object of the invention to provide an adhesive which has low odor characteristics.
It is another object of the invention to provide an adhesive which quickly forms a bond.
It is another object of the invention to provide an adhesive which will rebond for an extended period of time.
It is another object of the invention to provide an adhesive which forms an aggressive bond when cured.
It is another object of the invention to provide an adhesive which retains a rubbery, flexible condition when fully cured.
These and other objects, of the present invention are achieved in the preferred embodiments disclosed below by providing a reduced density, low water, high-solids flooring adhesive, comprising an intimately blended mixture of between 10 percent and 20 percent by weight of a high solids acrylic polymer characterized by having at least 70 percent by weight solids, between 10 and 20 percent vinyl-acetate ethylene, between 10 percent and 20 percent of a tackifying resin for increasing initial adherence of the adhesive to the flooring, between 40 percent and 60 percent filler, between 0.25 and 2 percent of a gas, wherein the total amount of solids is no less than 80 percent by weight.
According to one preferred embodiment of the invention, the adhesive includes between five percent and ten percent of a solvent.
According to another preferred embodiment of the invention, the adhesive includes an effective amount of an emulsifier and a plasticizer.
According to yet another preferred embodiment of the invention, the filler is selected from the group consisting of calcium carbonate, barium sulfate, and hydrated aluminum silicate.
According to yet another preferred embodiment of the invention, the gas is formed as a decomposition product of hydrogen peroxide.
According to yet another preferred embodiment of the invention, the hydrogen peroxide is initially present during mixing at a rate of 0.5 percent by weight of the adhesive.
According to one preferred embodiment of the invention, a low water, high-solids, solvent-free content flooring adhesive is provided, comprising an intimately blended mixture of between 10 percent and 20 percent by weight of a high solids acrylic polymer characterized by having at least 70 percent by weight solids, between 10 percent and 20 percent of a tackifying resin for increasing initial adherence of the adhesive to the flooring, between 40 percent and 60 percent filler, and a gas formed as a decomposition product of hydrogen peroxide, an effective amount of an emulsifier, and an effective amount of a plasticizer, wherein the total amount of solids is no less than 80 percent by weight.
According to yet another preferred embodiment of the invention, the acrylic polymer comprises 16 percent by weight, the tackifying resin comprises between 10 and 11 percent by weight, the filler comprises 51 percent by weight.
According to yet another preferred embodiment of the invention, the density of the adhesive is approximately 13 pounds/gallon.
According to yet another preferred embodiment of the invention, the total amount of solids is no less than 80 percent by weight.